The research areas covered by the Alveolar Biology Program include: 1) definition of the structural and functional properties of the alveolar lining layer in the adult lung and also at birth; 2) investigation of the biosynthetic processes of the alveolar cells and subcellular components; 3) investigation of the interrelationship between alveolar epithelial cell and surface biology, and airway epithelial surfaces; 4) identification of the surfactant system in fetal pulmonary fluid, its maturation during fetal development and its formation of the alveolar lining layer at birth; and 5) studies of fetal pulmonary fluid and solute dynamics vis a vis the flux alveolar space and pulmonary capillary in the developing fetus. Research highlights for the period of this report include: 1) development of methods for isolation and recovery of pulmonary secretory IgA and free secretory component; 2) in vitro definition of surface tension of the pulmonary surfactant (dipalmitoyl phosphatidylcholine) under conditions of pH, temperature and humidity that exists in situ; 3) verification of the importance of the acyl transferase pathway for the synthesis of dipalmitoyl phosphatidylcholine; 4) isolation of alveolar type I cell in vitro; 5) verification of the efficacy of mechanical cutaneous stimulation for the induction of regular spontaneous breathing in the fetus; 6) establishment of the early neonatal "foam lung" as the essential transitional state from fetal liquid lung to neonatal air lung at birth; 7) definition of cardiopulmonary and metabolic effects of acute exposure to phosgene.